I have my alarm go off at 06:30 everyday, including weekends.
Obviously I wake at those times on a week day for work, but on the weekend it will wake me up. But then I will simply snooze the bugger for 30 mins to further my sleep.
Now, you are probably thinking '7am!! ON A WEEKEND!'. Well, yes...
I wake at 7, feeling refreshed from that extra bit of sleep and guess what, I have a whole day to do stuff, not 5 hours of daylight due to waking at 1pm, but a whole 12 hours if no more of time to spend doing anything I planned out.
Sure, some weekends you just stay in bed until the afternoon, but once in a while, why not?
My point is, I have done this for a year now, as I was the same, all be it, shattered in the afternoons, followed by a nap after dinner then I would be wide awake until 2am!!
But after being strict with my self, as in no naps in the afternoons, awake in the morning. Eventually my body has gotten used to having 8-6 hours sleep and I have energy!
Plus, the correct diet helps as well.
Oh, and I never get tired at work anymore

Used to hate almost falling asleep as my desk, but now I couldn't if I tried.